1. Field of the Invention
This invention relates to a system for abating the smoke containing particulate matter (PM) (i.e., liquid droplets of grease or fat) and volatile organic compounds (VOCs) generated from the burning of fats, greases, proteins, and/or carbohydrates, during food preparation. More particularly, this invention is concerned with restaurant emissions smoke abatement using a rotary regenerative thermal or catalytic oxidizer.
2. Related Art
In the treatment of restaurant emissions except for chain-driven charbroilers, restaurant catalysts are normally installed inside the exhaust duct of a cooking ventilation system at a position close to the exhaust hood outlet. Due to the mixing with cool room air, the hot exhaust generated from the cooking process is significantly cooled before it reaches the exhaust hood. To initiate thermal or catalytic oxidation, the exhaust gas stream is needed to be reheated back to higher temperatures more conducive to either thermal or catalytic oxidation of the cooking exhaust contaminants. The additional heat is applied either directly on the catalyst support or to the exhaust gas stream. In addition to the preheating, the exotherm generated by the catalytic oxidation reaction also elevates the temperature of the exhaust gas. This often makes the temperature of the gas coming out of the catalytic reactor exceed the temperature operation limitation of the exhaust fan located at the end of the ductwork. To resolve this problem, outside makeup air is typically introduced into the duct before the fan to lower the exhaust temperature. Therefore, the capacity of the exhaust fan is undesirably increased to handle the extra load of air flow. The high costs of additional heating and oversized exhaust fans often hinder the use of catalytic systems for restaurant emission control.
U.S. Pat. No. 4,138,220 describes an apparatus for catalytic oxidation of grease and fats in low temperature fumes. The apparatus recovers at least some of the heat energy of the treated, exiting stream as heat from this stream is transferred to the entering stream prior to passage over the catalyst. The heat exchange device describes is a countercurrent heat exchanger, separate and apart from the catalyst. However, this patent is silent with regard to a heat exchange device for recovering heat exiting the apparatus which rotates and is an integral part of the catalyst system, i.e., the catalyst in the '220 patent is not deposited in or on the heat exchange device.
Applicants provide an advance over the prior art in the treatment of restaurant emissions by providing a rotary heat exchange device for thermally or catalytically destroying restaurant emissions. The advantages of which are herein below described.